female demon, late 14c., from Latin lamia "witch, sorceress, vampire," from Greek lamia "female vampire, man-eating monster," literally "swallower, lecher," from laimos "throat, gullet" (see larynx). Perhaps cognate with Latin lemures "spirits of the dead" (see lemur) and, like it, borrowed from a non-IE language. Used in early translations of the Bible for screech owls and sea monsters. In Middle English also sometimes, apparently, mermaids:

Also kynde erreþ in som beestes wondirliche j-schape, as it fareþ in a beest þat hatte lamia, þat haþ an heed as a mayde & body as a grym fissche[;] whan þat best lamya may fynde ony man, first a flatereþ wiþ hym with a wommannes face and makeþ hym ligge by here while he may dure, & whanne he may noferþere suffice to here lecherye þanne he rendeþ hym and sleþ and eteþ hym. [John of Trevisa, translation of Bartholomew de Glanville's "De proprietatibus rerum," 1398]